Electrical precipitating apparatus

ABSTRACT

An electrical precipitating apparatus for removing particles from a gas stream having a housing defining a passageway for the gas stream and containing an electrode system therein comprised of discharge and collecting electrodes, which coact to effect precipitation of charged dust particles from the gas stream, the apparatus including baffle means located transverse to the gas passageway in the lower portion of the housing which baffle means extend upwardly beyond the lower end of the discharging electrodes toward the lower end of the collecting electrodes, thereby establishing a positive barrier to undesirable gas flow through the lower portion of the housing.

llnfite Stas atet H 1 Huppi Dec. 10, 1974 ELECTRICAL PRECIPITATING APPARATUS [75] Inventor: Xaver Johann Huppi, Zurich,

Switzerland [73] Assignee: Elex Limited AG, Zurich,

Switzerland [22] Filed: Feb. 16, 1972 [21] Appl. No; 226,856

[52] US. Cl 55/112, 55/128, 55/147, 55/148 [51] Int. Cl. B03c 3/76 [58] Field of Search 55/147, 112, 128, 129, 55/130, 140, 148, 154, 136, 137

[56] References Cited UNITED STATES PATENTS 1,329,237 1/1920 Fisbie 55/148 X 1,766,422 6/1930 Wintermute et a1... 55/136 X 2,192,250 3/1940 White 55/108 X 2,225,677 12/1940 White 55/154 X 2,275,001 3/1942 Anderson 55/130 2,634,318 4/1953 Wintermute.... 55/138 X 3,354,617 11/1967 Hoisington 55/112 X 3,444,668 5/1969 Masuda 55/126 X 3,509,695 5/1970 Egan et a1 55/120 FOREIGN PATENTS OR APPLICATIONS 228,915 6/1960 Australia 55/124 OTHER PUBLICATIONS Electrostatic Precipitators by Western Precipitation, Catalog Number P138, Western Precipitation Group, Joy Manufacturing Company, 1000 W. 9th Street, Los Angeles, Calif. 90015, 12 pages received in Patent Office Oct. 16, 1968.

France 55/140 Germany 55/112 Primary ExaminerDennis E. Talbert, Jr.

[57] ABSTRACT An electrical precipitating apparatus for removing particles from a gas stream having a housing defining a passageway for the gas stream and containing an electrode system therein comprised of discharge and collecting electrodes, which coact to effect precipitation of charged dust particles from the gas stream, the apparatus including baffle means located transverse to the gas passageway in the lower portion of the housing which baffle means extend upwardly beyond the lower end of the discharging electrodes toward the lower end of the collecting electrodes, thereby establishing a positive barrier to undesirable gas flow through the lower portion of the housing.

1 Claim, 1 Drawing Figure 1 ELECTRICAL PRECIPITATING APPARATUS BACKGROUND OF THE INVENTION The present invention is directed to electrically precipitating suspended particles from a dirty gas stream. More specifically, it is concerned with improvements in an apparatus of the type in which the dirty gas stream 'is passed through a charging and collecting electrical field to effect precipitation of charged particles. Since there are only'two types of electrodes defining one electrical field within the apparatus, the apparatus is termed a single stage precipitator. The primary components are discharge electrodes and collecting electrodes. A discharge electrode is an electode which has, at a given point in time, a corona discharge emanating therefrom due to its configuration and high electrical potential. While, at a second point in time', the electrode may have a lower electrical potential and no corona. Such an electrode may be a small diameter wire or a rod provided with sharp edges or points which may function to concentrate electric charges on its surface and thereby cause an electric corona.

The present invention is also applicable to two stage precipitators. Two stage precipitators are different from single stage precipitators in that two distinct electrostatic fields are formed, one adjacent discharging electrodes, and the other between precipitating electrodes and collecting electrodes. A precipitating electrode is an electrode which is maintained at an electrial potential, but minimizes or suppresses corona discharge therefrom. Such a precipitating electrode is generally of a configuration which is free from sharp corners, edges, or points. Generally, a precipitating electrode is maintained at a voltage which is less than the voltage of a corresponding discharge electrode. The particles to be removed are charged by a corona discharge near the discharge electrode and travel into the field of the precipitating electode where they are precipitated on a non-discharging collecting electrode.

One major problem in all electrostatic precipitators is eliminating currents of gas around the electrode system. Particularly, troublesome is any gas flow into and out of the lower hopper portion of the precipitator. Such gas fiow may subsequently pass out the clean gas outlet carrying particles previously collected in the hopper or it may dislodge and remove particles previously deposited on the lower portions of the collecting electrodes. This undesirable gas fiow into and out of the hopper accounts for considerable loss in overall cleaning efficiency. The present invention solves the problem of such loss of overall cleaning efficiency, in both two stage and single stage electrostatic precipitators.

SUMMARY OF THE INVENTION stream of gas, the lower portion of the housing defining a hopper below the passageway; an electrode system in the passageway, comprising a grounded collecting electrode structure and a high voltage discharge structure,

extending longitudinally in the passageway, parallel to and transversly spaced from, the collecting electrode structure. The discharge electrode structure includes vertically disposed discharge electrodes spaced longitu dinally from the gas passageway and creating charging fields extending trasversly of the gas passageway in longitudinally spaced vertical planes. The discharge electrodes can be further defined in that they are maintained in their relative positions by weights secured to their ends. The weights are separated and positively positioned with respect to one another by a spacing frame having a dividing slot therein. The apparatus also contains baffle means transverse to the gas stream which extends upwardly through the dividing slot in the discharging electrode spacing frame at least to the horizontal plane defined by the lower edges of the gas inlet and the gas outlet, toward the lower edges of the collecting electrodes. The apparatus can be further defined in that the distance between the baffle means and the discharge electrode weights and spacing frame is such that there is no arcing therebetween.

The electrical precipitating apparatus of this invention has been found to be effective in reducing the overall dust particle concentration over the prior art accepted level. In this regard it is appreciated that particle removal from a gas stream can be effected in a variety of ways. Each of such ways will have a lower limit. However, it is important to realize that to go beyond the various lower limits and obtain a super-clean gas stream is extremely difficult. However, the present invention provides a straightforward, inexpensive, readily constructed and easily maintained apparatus for electrical precipitation of dust particles to a concentration lower than heretofore thought possible.

DESCRIPTION OF THE DRAWING FIG. 1 is a cross-sectional elevational view of the electrical precipitating apparatus of this invention.

PREFERRED EMBODIMENT Housing 10 includes opposed gas inlet 11 and gas outlet 12 which define a gas passageway A therebetween in housing 10 through which dirty gas travels. Gas inlet 11 and gas outlet 12 are equal in size and are located on opposite sides of housing 10. Gas inlet 11 and gas outlet 12 have their lower respective edges 14 and 16 lying in the same or common horizontal plane. Housing 10 further includes in its lowermost portion, hopper 17 and disposed thereabove in gas passageway A of housing 10 is an electrode system 18. Electrode system 18 includes grounded collecting electrodes 22 which extend longitudinally in spaced planes parallel the direction of gas flow and high tension discharge electrodes 24 which extend in successively spaced relation to provide spaced rows of discharge electrodes be tween the spaced rows of collecting electrodes 22.

Discharge electrodes 24 are suspended from the upper portion of housing 10 by suspension means 19. Collecting electrodes 22 are supported by rapping bars 32 and 30 which rest on electrode ledge support means 21 fastened at their extremities to housing 10. Discharge electrodes 24 cause a charging field to be present within housing 10. Discharge electrodes 24 terminate at their lower ends in discharge electrode weight 28. It is to be noted that discharge electrode weights 28 are spaced equidistant from one another by a suitable, substantially rigid spacing frame 29. Spacing frame 29 has a dividing slot 31 therein. Dividing slot 31 divides spacing frame 29 into two equal sized segments. The,

principal function of the dividing slot 31 is more fully explained below. It should also be noted that the lower rapping means member 30 for each collecting electrode 22 does not extend below the horizontal plane defined by the lower edges of gas inlet 11 and gas outlet 12. I

Housing additionally contains vertical baffle means 33 which extends from the lowermost portion of hopper 17 upward transverse to the air flow path A toward rapping means member 30. In accordance with the present invention, baffle means 33 passes between dividing slot 31, so as to be spaced at a distance which is calculated to insure that no arcing will occur between the discharge electrodes 24 or discharge electrode weights 28 or the spacing frame 29.

In the operation of this invention, dirty gas enters dirty gas inlet 11 and passes through passageway A where it is cleaned by electrode system 18 and ultimately passes through gas outlet 12. Cleaning is effected by the electrostatic precipitator apparatus disclosed herein in a manner which is disclosed and understood by the prior art. Briefly, the particles of dust in the gas stream are ionized when they pass into the charging field which surrounds discharge electrodes 24. These charged particles are carried along in the air stream until they encounter one of collecting electrodes 22. The collecting electrical field adjacent collecting electrodes 22 is strong enough to cause the charged particles to be attracted thereto. The particles deposit upon collecting electrodes 22 to be later removed. Such removal may be effected by rapping, vacuuming, or scrubbing collecting electrodes 22. Rapping bar means members are shown in FIG. 1. They are activated by an activation system not shown. The removed particles fall into hopper l7 where they are collected and retained until outlet 34 is opened and hopper 17 is emptied.

The concentration of particles which are contained in the gas passing along the rapping means members 30 and 32 just outside of passageway A is much greater than the concentration of particles in the cleaned gas which passes along lower rapping means member 30. Applicant has successfully reduced the concentration of dust particles in the gas passing along lower rapping means member 30 by providing baffle means 33 which extend upwardly from the lowermost portion of hopper 17 through dividing slot 31 beyond discharge electrode weights 28 to contact rapping means member 30. It is important to note that inlet 11 and outlet 12 have their lower edges 14 and 16 lying in the same horizontal plane through housing 10. Rapping means member 30 can then be movably secured to these lower edges and baffle means 33 can extend upwardly to slidably engage the lower side of rapping means member 30. Such anarrangement affords a positive reduction in the concentration of dust particles since it essentially blocks off any air flow stream below the active portion of electrode system 18. This reduction in dust concentration can only be accomplished if dividing slot 31 is employed to provide access through spacing frame 29.

It will be noted that any gas circulating means can be used to move the dirty air through housing 10. Specifically, a fan or other blower would be connected to inlet 11 or outlet 12 to move air to be cleaned in a horizontal direction through housing 10. However, it is also possible that a stack gas stream would be passed through housing 10 to be cleaned.

Having thus described the invention what is claimed is:

1. An electrical precipitating apparatus for removing suspended particles from a gas comprising: a housing having an opposed gas inlet and a gas outlet and defining a passageway for a stream of gas; the lower portion of said housing defining a hopper below said passageway with the lower edges of the gas inlet and gas outlet lying substantially in a common horizontal plane; an electrode system in said passageway including grounded collecting electrodes supported by rapping bars at both the top and bottom thereof said top supporting rapping bars resting on electrode ledge support means attached to said housing and said bottom supporting rapping bars also attached to said housing and extending to the plane defined by said lower edge of said gas inlet and outlet, said collecting electrodes extending longitudinally in spaced planes parallel to the direction of gas flow through said passageway, said electrode system further including high voltage discharge electrodes extending longitudinally in said passageway parallel with and transversely spaced from said collecting electrodes in successive relationship to provide spaced rows of discharge electrodes between the spaced rows of collecting electrodes, said discharge electrodes being spaced longitudinally of said gas passageway and creating charging fields extending transversely of the gas passageway in longitudinally spaced vertical planes, said discharge electrodes being further defined in that they are suspended from the upper portion of said housing by suspension means and maintained in their relative positions by weights secured to their lower ends said weights being separated and positively positioned with respect to one another by a spacing frame having a dividing slot therein; baffle means comprising a single flat sheet of material located equidistant from said gas inlet and said gas outlet supported within said housing transverse to said gas passageway and extending upwardly through said dividing slot in said discharge electrode spacing frame at least to the horizontal plane defined by the lower edges of the gas inlet and gas outlet, said apparatus being further defined in that the distance between said baffle means and said discharge electrode weights, and spacing frame is such that there is no arcing therebetween. 

1. An electrical precipitating apparatus for removing suspended particles from a gas comprising: a housing having an opposed gas inlet and a gas outlet and defining a passageway for a stream of gas; the lower portion of said housing defining a hopper below said passageway with the lower edges of the gas inlet and gas outlet lying substantially in a common horizontal plane; an electrode system in said passageway including grounded collecting electrodes supported by rapping bars at both the top and bottom thereof said top supporting rapping bars resting on electrode ledge support means attached to said housing and said bottom supporting rapping bars also attached to said housing and extending to the plane defined by said lower edge of said gas inlet and outlet, said collecting electrodes extending longitudinally in spaced planes parallel to the direction of gas flow through said passageway, said electrode system further including high voltage discharge electrodes extending longitudinally in said passageway parallel with and transversely spaced from said collecting electrodes in successive relationship to provide spaced rows of discharge electrodes between the spaced rows of collecting electrodes, said discharge electrodes being spaced longitudinally of said gas passageway and creating charging fields extending transversely of the gas passageway in longitudinally spaced vertical planes, said discharge electrodes being further defined in that they are suspended from the upper portion of said housing by suspension means and maintained in their relative positions by weights secured to their lower ends said weights being separated and positively positioned with respect to one another by a spacing frame having a dividing slot therein; baffle means comprising a single flat sheet of material located equidistant from said gas inlet and said gas outlet supported within said housing transverse to said gas passageway and extending upwardly through said dividing slot in said discharge electrode spacing frame at least to the horizontal plane defined by the lower edges of the gas inlet and gas outlet, said apparatus being further defined in that the distance between said baffle means and said discharge electrode weights, and spacing frame is such that there is no arcing therebetween. 